1. Field of the Invention
This invention relates to LINACs and more specifically this invention relates to a compact system and method to accelerate particles toward a physiological target or a non-physiological target.
2. Background of the Invention
Ion beam therapy is becoming a standard of care for treatment of tumors. Approximately one third of the world's 15,000 accelerators are used for tumor therapy and other medical applications.
There are currently three technologies being used for radiation oncology: gamma/electron beams, proton beams, and carbon ion beams. The gamma/electron beam approach is by far the most mature and advances in techniques continue to improve its effectiveness. However, these particles spread the dose over the entire volume of a target tissue, thereby creating radiation damage to healthy parts.
Protons and carbon ions deposit most of their energy in a small depth, called the Bragg peak. Protons and gammas have the same radiobiological effectiveness (low linear energy transfer) so that the expected gains of proton therapy are restricted to the increased dose localization.
By contrast, carbon ions have a narrower Bragg peak than protons and also a higher biological effectiveness in the Bragg peak relative to that in the entrance region. Carbon ions deliver high linear energy transfer which makes them more effective at treating radiation resistant hypoxic tumors. In addition, carbon ions can deliver even more localized doses than protons due to their heavier mass and the resulting reduced transverse scattering.
Carbon therapy is a promising technique for cancer treatment, given its clinical efficiency and reduced toxicity profiles. This is because carbon ions could be better localized in the tumor volume. The ion deposits most of its energy by ionization in a very short distance just before it stops. The most efficient treatment is achieved when the energy deposition volume is changed in all three directions as fast as possible for treatment of moving organs.
430 MeV per nucleon carbon beam (MeV/u) is required to cover the full penetration depth that is up to about 30 cm (about 12 inches) of the human body. Three technologies are available for ion beam acceleration: cyclotrons, synchrotrons, and linear accelerators (LINACS).
Both cyclotrons and synchrotrons are expensive and bulky constructions with large magnets. A cyclotron is a continuous wave fixed energy machine. “Continuous wave” means it produces beam continuously in contrast to a pulsed machine that produces bursts or bunches of beam. Fixed energy means the beam cannot be produced at variable energy, only one energy at the exit of the cyclotron. It does not offer the flexibility of adjusting the time structure or the energy of the beam by simple tuning.
Energy adjustments in cyclotrons require degraders, which are variable thickness solid materials. This process generates a large amount of radiation and significantly worsens the beam quality. The effect is unnecessary beam loss and radiation that requires adequate shielding.
Synchrotrons are circular structures which require large magnets that consume large amounts of power. Indeed, some state of the art synchrotrons have a perimeter of about 70 meters. Due to the multi-turn acceleration in a synchrotron, changing the energy may take a few seconds such that it is not effective for fast three dimensional tumor painting or treatment of moving organs.
State of the art linacs require a large foot print at a Hospital or University Campus, with some linacs exceeding hundreds of meters in length.
A need exists in the art for a system and method for efficient ion therapy in oncology scenarios. The system and method should penetrate all aspects of a patient while minimizing exposure to healthy tissue. The system and method should have a small foot print so as to not impose on valuable real estate in hospital or oncology center settings. The system should also be a single pass system so as to be capable of changing the beam energy very quickly. This cannot be easily achieved in a synchrotron because of the multi-turn and cyclic nature of those machines.